This invention relates to an electronic control circuit for use in heating and/or airconditioning systems of residences and buildings, and more particularly to an improved programmable, automatic-cycling control circuit for controlling the operation of heating and/or airconditioning systems.
In U.S. Pat. No. 4,049,193 entitled "Systems and Apparatus for Control of Fueled Heat Generators," apparatus and systems are disclosed for the control of heat generators during time intervals which are readily changeable by varying the settings of a plurality of switches by the user. A digital clock was provided for generating output signals indicative of the elapsed time of day, and control signals were generated in accordance with the switch settings set by the user of the desired times of day for the control of the system. Both night and day thermostats were employed, and were set to operate during predetermined time intervals in accordance with the desires of the user. Once the various time intervals were set, there was no provision for automatically adjusting the on-off timer of the thermostat in accordance with environmental conditions such as the rate of heating and cooling of a room which the thermostat was monitoring. In using such a system, the only way to adjust the on-off timer was by resetting the switches. For example, if the night thermostat was controlling until 7 a.m. and the day thermostat was switched on for a predetermined warm-up interval, once the interval was set, the thermostat would continue to operate until the temperature of the room was brought up to the level set on the thermostat, and probably a little more for "overshoot." The next mode of operation change would not occur until the warm-up period mode was completed. The only way to change the warm-up period would be to change the time interval for warm-up. Since the required warm-up period times change during the season, the period may be too long in the warmer weather, and too short in the colder weather, thus not supplying enough heat. Accordingly, seasonal adjustment is required under the system of the aforesaid patent.
Another problem with the aforesaid system is that a loss of line voltage shuts the system down, and the time sequences set in the electronic clock must be reset when the power goes back on in order that the heating system which is being controlled is enabled and disabled at the proper times. Another problem with the aforesaid system is the size, complexity and cost of the control unit. Another problem with the aforesaid system is that primary power, additional to and separate from the thermostat lines, was required to power the unit. This increased both the cost and time to install the system.